The present invention relates to an apparatus for optically record/regenerating or reproducing information, and in particular to an optical information record/regenerating apparatus provided with a track jump function for driving an optical system, for forming a light spot on an optical information recording medium, to move the light spot to a neighboring track.
For optical information recording and regeneration, there are already known media of various shapes such as disk, card and tape. Among these, a card-shaped optical information recording medium, hereinafter called an optical card, is expected to have a large demand as a compact, light and conveniently portable recording medium of a large capacity.
FIGS. 1A and 1B are respectively a schematic plan view and a front view of a driving unit of an optical information record/regenerating apparatus utilizing such optical card, wherein the optical card 1 is placed on a shuttle 2 fixed on a belt 3, which is supported by pulleys 4, 4'. The pulley 4 is rotated by a DC motor 5. Thus the shuttle 2 and the optical card 1 can be displaced in the direction of x-axis by the forward or reverse rotation of the motor 5.
Above the optical card 1, or in front of the plane of drawing in FIG. 1A, there is provided an optical head 6 which movably supports an optical system 7. Said optical system 7 is rendered movable by a small amount in the direction of y-axis (indicated by an arrow in FIG. 1A) by, means of an unrepresented driving device (such as a tracking coil), and a light beam 8 converged by said optical system 7 forms light spots S1 and S2 on the optical card 1. Consequently said light spots S1, S2 are slightly movable in the y-axis direction by said optical system driving device, whereby said light spots follow a track on the recording medium by a tracking control. Naturally said optical system driving device also executes a focusing control but the details thereof will be omitted in the present description.
The optical head 6 is penetrated by a screw 9 rotated by a stepping motor 10 to allow large movement in the y-direction. Consequently the optical head 6 can be displaced in the y-direction by a desired distance, by controlling the direction and angle of rotation of the stepping motor 10 with appropriate pulses.
Now reference is made to FIG. 2 for explaining the function of the above-explained optical information record/regenerating apparatus.
As shown in FIG. 2, the optical card 1 is provided with a recording area a, track jump areas b, c, d and tracking tracks T1-Tn arranged with an auxiliary tracks Tj1-Tj(n-1) are provided alternating with the tracks T1-Tn.
Said auxiliary tracks Tj1-Tj(n-1) are parallel to the tracks T1-Tn-1 and are spaced by a distance yj therefrom in the areas b and d, but are angled by .theta.t to the tracks tl-tn-1 in the area c.
In the following there will be explained the function of the optical information record-regenerating apparatus, utilizing such preformatted optical card.
At first, in the recording area a, the light spot S1 formed by the optical system 7 irradiates for example a track T1, and the reflected light is utilized for tracking control. Also the light spot S2 irradiates a data track positioned between the tracks T1 and T2, with a high power to form pits in case of information recording, or with a low power to regenerate the recorded information from the reflected light in case of information reading. Due to tracking control based on the light spot S1, the light spot S2 always scans a predetermined position of the data track to achieve exact information recording or reading. Arrows attached to the light spots S1 and S2 in FIG. 2 indicate that, when the optical card 1 is displaced negatively or positively in the x-direction by the rotation of the motor 5, the light spots relatively move in the positive or negative direction in the x-axis.
When the light spots S1, S2 reach the area b of the track jump area b, c and d, the optical system 7 is displaced by a small amount in the positive y-direction by the optical system driving device, so that the light spots S1 and S2 jump by a distance yj in the positive y-direction. Consequently the light spot S1 for tracking control irradiates the auxiliary track Tj1, and said device so displaces the optical system that said light spot S1 follows said auxiliary track Tj1. Upon reaching the area d, the light spots S1 and S2 jump by a distance yj in the positive y-direction, whereby the light spot S1 is shifted to a neighboring track T2. Simultaneously the motor 5 is reversed whereby the light spots S1 and S2 start to move relatively in the negative x-direction. These operations are conducted for example by suitable detecting means and a system controller. In this manner a recording or reading operation is initiated for the neighboring track, and following tracks are subsequently scanned in succession in this manner.
The light spots S1 and S2 can make access to a desired track of the recording area a for information recording or reading, through such track jump operation and relative movements of the optical head 6 in the x- and y-directions of the optical card 1, by means of the motor 5 and the stepping motor 10.
However, in practice, the moving direction of the optical card 1 may not be parallel to the tracks T1-Tn due to an error in the precision of the manufacture. The moving direction of the optical card 1 in this case and that of the optical head 6 and optical system 7 are respectively indicated by broken-lined x- and y-axes, in FIG. 2, and a skew angle between the x-axis and the tracks T1-Tn is indicated by .theta.s.
In the presence of such skew angle .theta.s, the optical system driving device moves the optical system in the positive y-direction, in response to the movement of the light spots S1 and S2 relative to the optical card 1, so as that the light spot S1 can follow a track. However, the optical system driving device can move the optical system 7 only within a limited range, beyond which the tracking control becomes impossible as the light spot S1 can no longer follow the track. Consequently, before the tracking control reaches such limit, there is conducted a head moving operation in which the stepping motor 10 moves the entire optical head 6 by a distance .DELTA.y in the positive y-direction, thereby returning the optical system 7 to its normal position within the optical head 6.
However, due to its large angular acceleration, the stepping motor 10 generates a large acceleration in the optical head 6 in the y-direction, thus resulting in a certain positional aberration between the light spot S1 and the track in said head moving operation. Particularly in the track jump operation when the optical system 7 has certain vibrations in the y-direction, the tracking control operation has to have a high sensitivity in order to accurately achieve the head moving operation. Also in the area c of the auxiliary track where the optical system is moving in the y-direction, the tracking control has to have a high sensitivity for moving the optical system 7 within a short time, in order to achieve accurate head moving operation.
On the other hand, a high sensitivity of the tracking control will activate the tracking control mechanism even for dust or a scar on the optical card 1, thus resulting in frequent mistracking.
For reducing the skew angle .theta.s in order to reduce the number of the head moving operations and to prevent such track derailments, there is required a higher precision for the optical card and the related mechanisms, thus leading to a higher cost of the system. Also such mistracking can be prevented by reducing the moving speed of the optical system 7 in the y-direction, but, for such purpose it becomes necessary to extend the area c or to reduce the speed of the shuttle 2 in the x-direction. The former will result in a corresponding reduction in the recording capacity of the optical card 1, while the latter will result in a loss in the record/regenerating speed.
FIG. 3 shows another card format, wherein a card 21 is provided with plural parallel tracking tracks T, which are continuous and do not show changes in the width or distance thereof, both in an information recording area A and a track jump area B.
Light spots Sb, Sc are so positioned as to partly or entirely cover different tracks T, which are mutually adjacent in case of FIG. 3 but need not necessarily be adjacent. An automatic tracking servo operation is conducted on a tracking error signal, obtained from the difference of the light spots Sb, Sc reflected by the optical card 21 and detected by suitable sensors, and a light spot Sa records and reads information.
The example shown in FIG. 3 lacks the auxiliary tracks shown in FIG. 2. Such auxiliary tracks Tj are effective when the tracking tracks are widely distanced. A long jump at a high speed requires a long time due to an overshooting phenomenon, and, in such case, auxiliary tracks Tj as shown in FIG. 2 allow to prevent this problem by shortening the distance of jump.
However, in case of a track pitch in the order to 20 microns, a direct jump to the neighboring track is possible without auxiliary tracks, as shown in FIG. 3. However, the example shown in FIG. 3 is also associated with the drawbacks at jumping operation as already explained in relation to FIG. 2.
Consequently, the object of the present invention is to provide an optical information record/regenerating apparatus which is not associated with the drawbacks arising out of the track jump operation regardless of the recording format of the optical information recording medium such as optical card.
The above-mentioned object can be achieved, according to the present invention, by an optical information record/regenerating apparatus provided with an optical system for forming at least a light spot on an optical information recording medium provided with plural tracks including a track jump area therein, and an optical head movably supporting said optical system for allowing said light spot to move at least to an adjacent track in said track jump area, and adapted to record or regenerate information both by a relative movement of said optical head with respect to said optical information recording medium, and by movement of the optical system within the optical head. However, movement of said optical head is prohibited while said light spot is located in said track jump area.
Absence of the movement of the optical head in the track jump area eliminates the positional aberration between the track and the light spot in the head moving operation. Consequently a stable track jump operation can be easily achieved, without increasing the sensitivity of the tracking control. Also the track control operation is stabilized without excessive reaction of the control mechanism to dust or scars on the recording medium, since the sensitivity of tracking control need not be particularly high.